To provide necessary data and information for studying the relationship between trace metal elements in seawater, river estuary water and river water and ecological environments as well as human activity, elemental analysis of trace amount of metals is needed. The apparatus for analyzing trace metal elements in seawater, river estuary water and river water consists of a sample processing device (separation and enrichment device) and a device for determination of trace metals. A concentrating column is a key component in the sample processing device.
CN application No. 200410021965.5 discloses an auto-analyzer for determination of trace metal elements in seawater and river estuary, the testing device of which is low pressure ion-chromatography, and the operating pressure is 2˜3×105 Pa. Two types of online sample processing devices and three types of concentrating columns are provided. One type of online sample processing device is a direct processing type and comprises a concentrating column, a low pressure pump, a switch valve, a sample container, a washing fluid container and a desorption fluid container, wherein the outlet of a low pressure pump is connected to the fluid inlet of a concentrating column via pipe fittings, the inlet of a low pressure pump is connected to the outlet of a switch valve via pipe fittings, the inlets of a switch valve are connected, via pipe fittings, to a sample container, a washing fluid container and a desorption fluid container respectively. For this type of online sample processing device, the column packing of the concentrating column is an iminodiacetic acid type macroporous adsorption resin or a spherical cellulose adsorbent for metals. The other type of online sample processing device is a complex processing type and comprises a concentrating column, a low pressure pump, a switch valve, a sample container, a washing fluid container, a desorption fluid container, a complexant container and a reactor. There are two low pressure pumps, one is connected between a concentrating column and a switch valve, with its outlet being connected to the inlet of a concentrating column and its inlet to the outlet of a switch valve both via pipe fittings; and the other is connected between the reactor and the sample container as well as a complexant container, with its inlet being connected to a sample container and a complexant container and its outlet to a reactor both via pipe fittings. The inlets of a switch valve are connected, via pipe fittings, to a washing fluid container, a desorption fluid container and a reactor respectively. For this type of online sample processing device, the column packing of the concentrating column is a C18 chemically bonded stationary phase.
In analyzing the trace metal elements in seawater and river estuary water, it is known that the column packing of concentrating column generally used is an iminodiacetic acid type macroporous adsorbent resin for high pressure ion chromatography and a C18 chemically bonded stationary phase for ICP-emission spectra.
As a packing material for concentrating columns, iminodiacetic acid type macroporous adsorbent resin has the following problems: (1) magnesium and calcium ions have to be removed by ammonium acetate solution and other interfering materials by deionized water before the desorption of trace metals since the magnesium and calcium ions are adsorbed to the concentrating column simultaneously during concentration; (2) there are difficulties during desorption and the desorption fluid used is 0.05˜0.20 mol/L HNO3 solution which brings undesired effects to the subsequent analysis of trace metal elements.
As a packing material for concentrating columns, a C18 chemically bonded stationary phase has the following problems: (1) the processing of samples is so complicated that the trace metals in test samples have to be reacted with a complexant (which is a solution of 8-hydroxyquinoline in ethanol) first to form a metal complex, and then be adsorbed to a concentrating column, after that, deionized water is used as a washing fluid to remove the remaining interfering material in the flow such as sodium chloride, magnesium and calcium, and finally a methanol-water-HNO3 solution is used for desorption, in which a metal complex adsorbed to a concentrating column enters a low pressure ion chromatography system of the device; (2) there is methanol, a toxic material, presents in the desorption fluid, and this is thus harmful to the operator.
Although a spherical cellulose adsorbent for metals does not have the disadvantages of the above-mentioned two packing materials, the process to prepare it is rather complicated.
In addition, the automation extent of the above-mentioned combination of online sample processing device and testing device during analysis is not satisfactory.